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Michael Ocampo via Flickr Creative Commons // CC BY 2.0
Michael Ocampo via Flickr Creative Commons // CC BY 2.0

How Tomatoes Fend Off Parasitic Vines

Michael Ocampo via Flickr Creative Commons // CC BY 2.0
Michael Ocampo via Flickr Creative Commons // CC BY 2.0

When medieval guards spotted invaders in the distance, they’d pull up the drawbridge and fortify their castle’s defenses. A horse that senses biting flies will flick its tail. The whine of a mosquito’s wings is our cue to start swatting. Plants under attack can’t do any of these things, but that doesn’t mean they’re helpless. Researchers say some tomato plants can sense and defend themselves against encroaching parasitic vines. They published their findings this week in the journal Science. 

Plants’ ability to converts sunlight into nutrients, combined with their inability to run away, makes them juicy targets for bugs, microbes, fungi, and parasitic vines. Experts estimate that parasitic plants alone cause billions of dollars of agricultural damage every year [PDF].

But plants aren’t going down without a fight. Many species have evolved physical defenses like thorns, while others turn to chemical warfare, pumping out terrible-tasting or toxic compounds as soon as they sense a threat. They’re vigilant monitors of chemical signals in their environments, and can even identify invading microbes by their molecules. One plant even farts in the face of danger.

Researchers wondered if the molecular ID technique could work against other types of parasites as well. They decided to test the concept on the tomato plant (Solanum lycopersicum) and one of its would-be adversaries, a vine called Cuscuta reflexa. We say "would-be" because, unlike many of its relatives, S. lycopersicum has somehow found a way to fend off the mooching vine.

C. reflexa on the susceptible tomato relative S. pennellii. Image credit: Eric Melzer

The key moment in host/parasite combat for C. reflexa happens when the vine is still young. Although its seeds are quite hardy, germinating C. reflexa seedlings are vulnerable and will die unless they can find and successfully colonize a plant host within a few days. That colonization can only happen if the parasite can quickly produce syringe-like feeding structures called haustoria that pierce the plant’s cell wall and suck out the nutrients within. To thwart the vine, then, a potential host has to stop the haustoria before they start. And to do that, it needs to know the parasite is there. 

To test the tomato plant's ability to sense its presence, the researchers clipped off small samples of its leaves and dropped them into beakers, to which they also added purified extracts of C. reflexa molecules. They also set up control beakers containing the C. reflexa essence and samples of other, more susceptible plants. Experimenters then took samples of the air inside the beakers and tested it to find out if the alarmed plants were releasing defensive chemicals. 

Sure enough, S. lycopersicum sensed the parasitic vine’s molecules and went into defensive mode. The other plants just kind of … sat there.

Molecular analysis of all the host plants revealed that S. lycopersicum alone contains a receptor protein that the researchers called CUSCUTA RECEPTOR 1, or CuRe1. 

Biologists Vardis Ntoukakis of the University of Warwick and Selena Gimenez-Ibanez of Spain’s Centro Nacional de Biotecnología were not involved in the research, but praised the team’s results. “The identification of CuRe1 represents a major breakthrough in understanding the strategies used by plants to sense danger from diverse origins,” they wrote in a commentary in Science.

They note that other types of parasites also rely on haustoria, and say it makes sense that hosts would use the same mechanisms to keep them all out.

“This work greatly advances our understanding of the mechanisms controlling plant resistance to parasitic plants while at the same time opening up new avenues of research.”

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People Listen (and Remember) Better With Their Right Ears, Study Finds
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If you’re having trouble hearing in a noisy situation, you might want to turn your head. New research finds that people of all ages depend more on their right ear than their left, and remember information better if it comes through their right ear. The findings were presented at the annual meeting of the Acoustical Society of America in New Orleans on December 6.

Kids’ ears work differently than adults' do. Previous studies have found that children's auditory systems can’t separate and process information coming through both of their ears at the same time, and rely more on the auditory pathway coming from the right. This reliance on the right ear tends to decrease when kids reach their teens, but the findings suggest that in certain situations, right-ear dominance persists long into adulthood.

To study how we process information through both our ears, Auburn University audiologists brought 41 adult subjects (between the ages of 19 and 28) into the lab to complete dichotic listening tests, which involve listening to different auditory inputs in each ear. They were either supposed to pay attention only to the words, sentences, or numbers they heard in one ear while ignoring the other, or they were asked to repeat all the words they heard in both ears. In this case, the researchers slowly upped the number of items the test subjects were asked to remember during each hearing test.

Instructions for the audio test read 'Repeat back only the numbers you hear in the right ear.'
Sacchinelli, Weaver, Wilson and Cannon - Auburn University

They found that the harder the memory tests got, the more performance varied between the ears. While both ears performed equally when people were asked to remember only four or so words, when the number got higher, the difference between their abilities became more apparent. When asked to only focus on information coming through their right ear, people’s performance on the memory task increased by an average of 8 percent. For some people, the result was even more dramatic—one person performed 40 percent better while listening with only their right ear.

"Conventional research shows that right-ear advantage diminishes around age 13, but our results indicate this is related to the demand of the task,” one of the researchers, assistant professor Aurora Weaver, explained in a press release. In other words, when the going gets tough, the right ear steps up.

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Pigeons Are Secretly Brilliant Birds That Understand Space and Time, Study Finds
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Of all the birds in the world, the pigeon draws the most ire. Despite their reputation as brainless “rats with wings,” though, they’re actually pretty brilliant (and beautiful) animals. A new study adds more evidence that the family of birds known as pigeons are some of the smartest birds around, as Quartz alerts us.

In addition to being able to distinguish English vocabulary from nonsense words, spot cancer, and tell a Monet from a Picasso, pigeons can understand abstract concepts like space and time, according to the new study published in Current Biology. Their brains just do it in a slightly different way than humans’ do.

Researchers at the University of Iowa set up an experiment where they showed pigeons a computer screen featuring a static horizontal line. The birds were supposed to evaluate the length of the line (either 6 centimeters or 24 centimeters) or the amount of time they saw it (either 2 or 8 seconds). The birds perceived "the longer lines to have longer duration, and lines longer in duration to also be longer in length," according to a press release. This suggests that the concepts are processed in the same region of the brain—as they are in the brains of humans and other primates.

But that abstract thinking doesn’t occur in the same way in bird brains as it does in ours. In humans, perceiving space and time is linked to a region of the brain called the parietal cortex, which the pigeon brains lack entirely. So their brains have to have some other way of processing the concepts.

The study didn’t determine how, exactly, pigeons achieve this cognitive feat, but it’s clear that some other aspect of the central nervous system must be controlling it. That also opens up the possibility that other non-mammal animals can perceive space and time, too, expanding how we think of other animals’ cognitive capabilities.

[h/t Quartz]

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